My husband got stung by a prickly cattapillar and it's swollen should we be concerned?

Probably not: Most of those catepillars are not dangerous. Their spines contain chemical irritants to discourage predators from eating them. The important thing is to watch for signs of infection like warmth, redness and an inrease in pain. You can also try some ice or a poultace of baking soda in water to help "draw out" the irritant.

Histamine release: A sting or bite typically causes release of histamine causing redness, swelling, itching, etc. Usually can control with cool compress, Benadryl (diphenhydramine) or claritin. If it causes shortness of breath, wheezing or lips to swell, seek attention. Thx.